This model calculates the heat flow by solar gains through each glazed element k. The heat flow is given by
Φsol,k =Fsh,k Isol,k gfac (1-Fframe) Awin,k
where Fsh,k is the shading reduction factor which is set to 0.9 by deafult, Isol,k is the solar irradiance per square meter of surface area, gfac is the total solar energy transmittance of the trasparent element, Fframe is the frame area fraction, and Awin,k is the overall area of the glazed element in square meters. The model neglects the extra heat flow due to thermal radiation to the sky from the building.